You can see the bar that is sort of in the grid pattern. If your main focus of the image is along these lines it will draw the eye to it. Having something dead center isn't as interesting as following the lines.
The first photo follows the top line while the other one uses more of the intersection of the grid lines.
Here the fish is the both on the grid and the bottom line. You do have to watch if you are cutting off people's heads on purpose or if things are coming "out" of their head. Our eyes see and focus on what we want to see but the camera just gets everything. Often one is surprised by what is on the photo.
Either by cropping a photo after it is taken or doing so as you are getting photos, you can fill the frame. This too draws the eye to the story. Remember the flower in the center at the beginning. This is the same flower but is much more interesting to view. You can also use the background to help frame what you see and how you do photos.
Think about the family reunion or gathering. What is it that you remember from past time? What do you need to keep your eye out for? You can have posed and informal photos. Think about the past memories and how you can gather them this time. Sometimes the background is part of the gathering and sometimes it isn't. What is it that you want to tell in the story of your scrapbook? If you plan ahead you will be amazed at what you will have to scrapbook!
You may want to put the grid lines on the camera or phone app to help you as you learn to see where the lines are. Practice with the camera and phone so that it is an extension of what you are so that it come naturally. Be careful that you don't stay behind the camera in a way that you don't react and take the time to be there with others. Enjoy the summer and gather photos like flowers to use in wonderful bouquets of images later.